The present invention relates to a clean robot which conveys wafers, reticles and the like in a clean room.
Semiconductor manufacturing apparatuses employ robots for clamping and conveying a wafer or a reticle out of a cassette, or conversely, putting them into the cassette. These robots work in a clean room.
In the clean robots, some arrangement to keep dust away from a driving transmission system within the robot body is necessary. Conventionally, the robots have comprised exhaust means for forcibly exhausting air in a casing to the outside of the clean room, as disclosed in Japanese Utility Model Publication No. 3-47834, or a magnetic fluid seal for completely sealing rotating portions as disclosed in Japanese Patent Laid-open No. 61-182787.
The exhaust means necessitates an exhaust unit for forcibly exhausting the air in the casing, which causes problems of cost and space. The magnetic fluid seal is advantageous because it does not need the forcible exhausting means. However, the fluid should be introduced around the rotating portions upon assembling and adjusting the robot. Otherwise, it should be introduced after the assembling and adjustment of the robot, i.e., the robot should be disassembled for introducing the fluid, and again assembled and adjusted. In the former setting, if the assembling adjustment process fails, the expensive magnetic fluid seal is wasted. Even though the fluid is used in the next assembling, its sealing capability is lowered since it may include dust raised in the previous assembling adjustment process. In the latter setting, the assembling and adjustment of the robot after setting of the seal increases the cost.
Another problem may arise when a sensor for detecting wafers or reticles is attached to the exterior of the robot a wiring member is introduced into the casing of the robot. In this case, dust must be prevented from the wire-introduced portion of the casing by sealing. Conventionally, the casing is holed for introducing the wiring member or a connector. After the wiring member or the connector is set, a sealing member is attached around the wiring member or the connector. Since the sealing member is attached with parts such as screws, the drawback arises that the number of parts for assembling the robot increases.
These robots conveying wafers or reticles are required to make "a linear conveying motion" in order to avoid breakage of the wafers or reticles. Conventional robots have realized this linear conveying motion by employing a timing belt as disclosed in Japanese Patent Laid-open No. 2-82550 and Japanese Patent Laid-open No. 2-83182, and a link mechanism as disclosed in Japanese Patent Laid-open No. 1-140738. Further, a robot having a motor and a reduction gear on its arm to control the movement as disclosed in Japanese Patent Application No. 3-215397 is known.
However, in the robots in Japanese Patent Laid-open Nos. 2-82550, 2-83182 and 1-140738, a transmission mechanism becomes complicated and it raises the cost. In the robot in Japanese Patent Application No. 3-215397, the motor for driving the second arm projects under the second arm, which is inconvenient when the robot is used in a limited working space such as in a semiconductor manufacturing apparatus.